Previous biochemical studies have indicated a role in DNA metabolism for the Escherichia coli DNA-binding protein. An approach to further elucidate the mechanism of action of this and similar proteins and to study its regulation is to determine how their levels fluctuate under various physiological conditions, following DNA-damaging procedures by chemicals or UV light and after bacteriophage infection. The E. coli DNA-binding protein also binds to some DNA polymerases and nucleases in the absence of DNA. These interactions will be further studied with respect to changes in enzymic properties and the association with other cellular proteins investigated. Similar experiments will be performed with the DNA-binding proteins induced by bacteriophage T7 and T3. Mutants of E. coli or of bacteriophage T7, defective in the DNA-binding protein will also be sought using a radioimmunoassay. In a collaborative project the molecular structure of some DNA-binding proteins, both in native form as well as a complex with oligonucleotides is being undertaken. Crystallographic analysis has already shown the dimeric nature of the fd gene 5 protein and given the basic shape of the molecule. The gross features of the unit cell of the protein:DNA complex have also been observed. Further study will enable the complete structure to be determined and the nature of the protein:nucleic acid interaction elucidated. A similar analysis of T4 gene 32 protein will also be undertaken. In bacteriophage T7 only eight phage genes appear to be involved in DNA replication. The role of genes 2, 2.5, 3, 3.5 and 6 in the formation and maturation of replicative intermediates will be investigated by an in vitro complementation reaction. DNA, made in cells infected with bacteriophage T7 mutant in one or more of the above genes, will be added to DNA-negative extracts of T7-infected cells and the fate of the DNA determined by physical techniques.